1.5 AS 90934 Demonstrate understanding of aspects of chemical reactions (4 credits)
COMBINATION REACTIONS
reactions of elements with other elements
NCEA PAST EXAM QUESTIONS on Combination
Two reactions that burn brightly were shown to a class. In Reaction 1, the teacher demonstrated a strip of magnesium ribbon reacting with oxygen in air.
In Reaction 2, which was shown on a video, a grey powder, zinc, was mixed with yellow sulfur powder. The mixture was poured into a pile and heated. The mixed powders burst into flame and made a white powder. Analyse these reactions by answering the following questions.
(a) Identify the type of reaction occurring, and state the condition that both reactions require for each to occur.
(b) Reaction 1: Magnesium metal reacting with oxygen gas in air.
(i) Describe the observations that would be made for this reaction.
(ii) Link these observations to the reactants and products involved in this reaction.
Reaction 2: Zinc metal reacting with sulfur.
(iii) Name the product formed when powdered sulfur reacts with powdered zinc metal.
(iv) Link the observations for this reaction, as given above, to the reactants and products involved.
(c) Explain the two reactions (magnesium ribbon with oxygen gas, and zinc powder with sulfur powder) in terms of electron transfer.
Write a balanced symbol equation for each reaction.
A teacher showed her class two video clips of chemical reactions. One was of a reaction between sodium metal and chlorine gas. The second was of a reaction between solid sulfur and chlorine gas.
(a) When the sodium metal reacted with chlorine gas, the video clip showed a shiny grey solid reacting with a yellow-green gas. The reaction resulted in the formation of white crystals. Link these observations to the reactants and products involved in this reaction.
(i) Name the product that will be formed when solid sulfur reacts with chlorine gas.
(ii) Identify the type of reaction that is occurring, and give a reason for your choice.
(b) (i) Write a balanced symbol equation for the reaction between sodium and chlorine.
(ii) Write a balanced symbol equation for the reaction between sulfur and chlorine.
(c) Explain the differences in the two reactions: sodium with chlorine gas and sulfur with chlorine gas, in terms of electron transfer.
A teacher demonstrates a reaction between hydrogen gas and oxygen in the air.
(i) Identify the type of reaction that occurs: Give a reason for your choice:
(ii) Describe any observations that would be made of this reaction, and link these to the substances involved in the reaction. Outline a test that could be used to confirm the presence of the product formed.
(iii) Write a balanced symbol equation for this reaction.
Different elements can be reacted together to form compounds with properties that are different to the original elements.
The reaction of iron and sulfur to form iron(II) sulfide is an example of a combination reaction where all species (reactants and products) have different properties. Give a detailed account of this combination reaction.
In your answer you should:
state the conditions required for this reaction to occur
describe any observations that would be made
outline the physical and chemical properties of EACH of the species
explain why the properties of the reactants differ from those of the products
write a balanced symbol equation for the reaction.
Chemical compounds are made by combining elements. For example, magnesium oxide is made by combining magnesium and oxygen, and carbon dioxide is made by combining carbon and oxygen.
Compare and contrast the combination reaction that produces magnesium oxide with the combination reaction that produces carbon dioxide. In your answer, you should:
state the conditions required for EACH combination reaction to occur
describe what would be observed in EACH combination reaction
write a balanced symbol equation for EACH combination reaction
discuss the similarities and differences between the TWO combination reactions.
hydroxides of copper, iron(II), calcium, barium and magnesium
carbonates of copper, iron(II), calcium, barium, magnesium, zinc, and lead.
NCEA PAST EXAM QUESTIONS on Exchange/Precipitation reactions
Various solutions were mixed in three separate beakers. Only two of the mixtures produced precipitates.
Identify the name, formula and colour of any precipitate that may have formed in the beakers
Justify the formation, or lack of formation, of precipitates in each of the three beakers. In your answer you should:
• identify the ions present in each solution before they are mixed
• explain why precipitates form or do not form
• write a balanced ionic or symbol equation for each of the precipitates formed.
You may leave spectator ions out of your equations.
An experiment in a school laboratory involves adding colourless solutions together as shown in the diagram below.
Analyse the reactions that occur in test tube A and test tube B. In your answer:
• record any observations you would make, and link these observations to the products formed in each reaction
• identify the type of reaction occurring in test tube A and test tube B, and justify your choices
• write a balanced ionic equation for each reaction.
The water in a swimming pool contains chloride ions as a result of adding chlorine to help keep the water safe to swim in.
Outline how you could test that there are chloride ions in the swimming pool. In your answer you should:
• describe what you would do to test for chloride ions
• identify the type of reaction and explain how this reaction helps identify the chloride ions
• describe all observations and link these to the chemical species involved
• write a balanced ionic equation for the reaction.
A chemical reaction occurs when a solution of calcium nitrate is added to a solution of sodium hydroxide. Analyse this reaction by:
describing any observations that would be made
identifying the products
explaining what happens to EACH ion that is present in these two solutions
writing a balanced symbol equation for this reaction. (Spectator ions may be omitted.)
Two solutions are mixed in one beaker and two different solutions are mixed in another beaker, as shown below. A precipitate forms in one of the beakers.
Identify the beaker in which a precipitate would form and justify your choice. In your answer, you should:
state which beaker the precipitate would form in
name the ions present in that beaker before they are mixed
name the precipitate formed (use the solubility rules in the resource booklet)
write a balanced symbol equation for the precipitation reaction
fully explain why no other precipitate will form in that beaker.
When a fresh solution of iron(II) sulfate is added to a solution of potassium carbonate, a precipitate forms. Discuss the process of this precipitation reaction.
FeSO4(aq) + K2CO3(aq) → ? In your answer:
State any observations you would make.
Explain what happens to each ion present in the solutions used in this reaction.
Write the name or formula of the precipitate formed.
Write a balanced equation (spectator ions may be omitted).
Refer to the solubility rules provided in the Resource Booklet.
Discuss what happens when a solution of potassium hydroxide is added to a solution of calcium nitrate.
KOH(aq) + Ca(NO3)2(aq) → ?
In your answer:
describe the observations you would make
predict the products that will form
explain what happens to each ion present in the solutions used in this reaction
write a net ionic equation for the precipitation reaction.
Each of the following equations shows what could happen when two solutions are mixed in a beaker.
Use the solubility rules in your Resource Booklet to identify which reaction would form a precipitate. Justify your answer by:
identifying the ions present in each solution before they are mixed
identifying the precipitate formed when the solutions are mixed
explaining why that precipitate forms.
1) The following pairs of solutions are mixed. Use the solubility rules in your Resource Booklet to identify if a precipitate is formed.
(a) Write the name of the precipitate. If none is formed, write no precipitate.
(b) Write a balanced equation for the formation of ONE precipitate identified in (a) above. Spectator ions may be omitted from ionic equations.
2) lead nitrate + potassium chloride → +
3) A colourless solution of barium nitrate is added to a pale green solution of iron(II) sulfate in a beaker. A reaction occurs.
(a) Describe the observations that would be expected for this reaction.
(b) State what type of reaction is occurring.
(c) Discuss the chemistry of this reaction. Your discussion should refer to the observations you made in part (a). Include a balanced equation in your answer. Spectator ions may be omitted.
The following solutions are mixed in the pairs shown. Use the solubility rules in your Resource Booklet to identify the precipitate (if any) that is formed for each pair.
(a) Write the name of the precipitate or, if none is formed, write no precipitate.
(b) Write a balanced equation for the formation of ONE precipitate identified in question (a)above. Spectator ions may be omitted from ionic equations.
The following pairs of solutions are mixed. Use the solubility rules in your Resource Booklet to identify the precipitate (if any) that is formed. Write the name of the precipitate or, if none is formed, write no precipitate.
Write a balanced equation for the formation of ONE precipitate identified in question (a) above. Spectator ions may be omitted from ionic equations.
magnesium chloride + sodium hydroxide → + _
Iron (II) nitrate solution is added to sodium hydroxide solution in a test tube. (i) Describe ONE observation that you would make as the reaction occurs.
(ii) Explain why your observation occurred.
(iii) Write a balanced ionic equation for this reaction.
1) Complete the table below by writing the name of the precipitate, or no precipitate if one is not formed. Use the Solubility Rules in the Resource Booklet.
thermal decomposition of hydroxides, carbonates and hydrogen carbonates
catalytic decomposition of hydrogen peroxide
NCEA PAST EXAM QUESTIONS on Decomposition
Two decomposition reactions were set up in the laboratory. Reaction 1: Solid sodium hydrogen carbonate, NaHCO3, was heated over a Bunsen burner flame.
Describe any observations that would be made as this reaction occurs, and link these to the reactants and products involved in the reaction.
(ii) Outline a test that could be used to confirm the presence of one of the products formed.
Write a balanced symbol equation for the decomposition of sodium hydrogen carbonate, NaHCO3.
Reaction 2: Test tube 1 and test tube 2 were both half-filled with hydrogen peroxide solution, H2O2. Some powdered manganese dioxide, MnO2, was then added to test tube 1. (c) Compare the observations you would make for the reactions in the two test tubes. Link these observations to the reactants and products involved in the reactions. (d) Write a balanced symbol equation for the reaction in test tube 1.
Compare and contrast the decomposition reactions shown in Reaction 1 (sodium hydrogen carbonate, NaHCO3) and Reaction 2 (hydrogen peroxide, H2O2).
Two calcium compounds were heated over a Bunsen burner in a school laboratory. In the first experiment, shown in the diagram below, calcium carbonate was heated. In the second experiment, calcium hydroxide was heated.
Compare and contrast the reaction that occurs when solid calcium carbonate is strongly heated, with the reaction that occurs when solid calcium hydroxide is strongly heated. In your answer:
• identify the type of reaction that occurs when each substance is strongly heated, and justify your choice
• describe any observations that would be made in each reaction, and link these observations to the reactants and products involved
• explain how the gas formed in each reaction could be identified
• write a balanced symbol equation for each reaction.
1) In a reaction, a boiling tube with copper carbonate powder is heated over a Bunsen burner flame.
(i) Identify the type of reaction that occurs: Give a reason for your choice:
(ii) Describe any observations that would be made of this reaction, and link these to the substances involved in the reaction.
Outline a test that could be used to confirm the presence of ONE of the products formed.
(iii) Write a balanced symbol equation for this reaction.
2) Two test tubes were set up in a school laboratory. Both test tubes were half-filled with identical solutions of hydrogen peroxide (H2O2).
It was observed that a few small bubbles of a colourless gas formed on the sides of each test tube.
Some solid manganese dioxide (MnO2) was added to test tube B.
(a) Describe the observations you would make after manganese dioxide (MnO2) was added to test tube B.
(b) Explain the chemistry of this reaction. In your answer you should:
• identify the type of reaction that happens in test tube B
• justify your choice of the type of reaction
• link the observations made for the reaction in test tube B to the substances involved in the reaction
• write a balanced symbol equation for the reaction involving hydrogen peroxide.
Students in a laboratory are asked to identify three powders by using a thermal decomposition reaction. The powders are copper hydroxide, Cu(OH)2, sodium carbonate, Na2CO3, and sodium hydrogen carbonate, NaHCO3. Explain how you could identify each of these powders by heating them.
Your answer should include:
any observations that would be made
any tests that would be carried out on products formed to confirm their presence
balanced symbol equations for any reactions occurring.
1) A group of students carried out an investigation into whether or not various solid carbonates undergo thermal decomposition. The students found that copper (II) carbonate did decompose when heated. Discuss the thermal decomposition of copper (II) carbonate. In your answer, you should:
name the products formed
describe what would be observed during the decomposition
explain why a solution of limewater would be useful in this investigation
fully explain what happens to the carbonate ions in the decomposition reaction
write a balanced chemical equation for the decomposition reaction.
2) A solution of hydrogen peroxide decomposes into water and oxygen gas very slowly.A catalyst can be used to speed up this reaction. The sketch graph below shows the volume of oxygen produced over the course of time when a catalyst is use
Discuss the decomposition of hydrogen peroxide using a catalyst. In your answer, you should:
name a catalyst that would be suitable for this reaction
describe what would be observed during the decomposition reaction
explain why only a small amount of catalyst is needed to catalyse this decomposition reaction
fully explain what happens in the catalytic decomposition of hydrogen peroxide over time as shown in the graph above.
Three carbonate compounds, sodium carbonate, zinc carbonate and copper carbonate, are heated one at a time in the apparatus shown in the diagram below.
(a) Complete the following table for the above reactions.
(b) Discuss the differences in the decomposition of sodium carbonate, zinc carbonate, and copper carbonate.
Describe the differences between the reactions of the three carbonates.
Link the relevant species to the observations you recorded in the table in (a).
Include any balanced equations.
Some green copper(II) carbonate powder is heated in a boiling tube over a Bunsen flame. A burning splint inserted into the top of the boiling tube goes out.
Discuss the chemistry in this thermal decomposition reaction by:
describing ONE other observation that would be made during this reaction
linking the observations to the relevant chemical species
writing a balanced equation.
Some dry copper(II) hydroxide was heated in a test tube over a Bunsen burner. When a piece of blue cobalt chloride paper was held in the mouth of the test tube, the paper turned pink. Discuss what happened in the reaction in the test tube.
Your answer should include any observations that would occur, and link all the observations to the reactants and products involved. Include an appropriate balanced equation in your answer.
A small amount of zinc hydroxide is heated in a test tube over a Bunsen burner. The following reaction occurs.
(a) State what type of reaction is occurring.
(b) Fully describe the observations that would be expected if this reaction was carried out in a school laboratory. Remember to link your observations to the substances involved.
A group of students carried out an investigation into the thermal decomposition of the following solid carbonates: sodium carbonate, calcium carbonate, and copper carbonate.
(a) Describe the appearance of each carbonate before it was heated.
(b) Describe the observations the students would have made when heating each of the carbonates.
(c) Write a balanced equation for the thermal decomposition of copper carbonate.
1) copper hydroxide (heat) →
2) A sample of copper carbonate is heated strongly in a boiling tube fitted with a delivery tube. The gas formed is bubbled into limewater. (See the diagram below.)
(i) Describe TWO observations, other than bubbles of gas, that would be made:
(ii) Write a balanced equation for the reaction that occurs when copper carbonate is heated:
displacement of metals ions in solution by other metals
NCEA PAST EXAM QUESTIONS on Displacement
A zinc rod was placed in a solution of copper sulfate, and another zinc rod was placed in a solution of magnesium sulfate. Both were left for one week
Describe any observations that would be made for each beaker. Identify the type of reaction that is occurring above.
Explain any difference in the observations made in Beaker 1 and Beaker 2 by linking your observations to the type of reaction occurring, and the reactants and products involved. Write ONE balanced ionic equation for a reaction from (a).
In the laboratory the teacher made impure lead crystals by placing a metal in lead nitrate solution
(i) Choose a suitable metal for this reaction and justify your choice.
(ii) Write a balanced ionic equation for the reaction you have chosen above
A spotting tile was set up, as shown in the diagram below, to investigate the reaction of small pieces of cleaned metals with a small volume of different metal nitrate solutions.
Complete the table below to identify which reactions will occur. You may refer to the activity series in the resource booklet.
(b) Identify the type of reaction that is occurring on the spotting tile, and justify your choice. In your answer:
identify the reaction you have selected
describe any observations that would be made in the selected reaction, and link your observations to the reactants and products involved in the reaction
identify the type of reaction occurring, and justify your choice write a balanced symbol equation for your reaction.
Explain why magnesium nitrate solution does not react with any of the three metals zinc, copper and lead.
You may refer to the activity series in the resource booklet.
An experiment in the laboratory involves placing an iron nail in copper sulfate (CuSO4) solution and a copper nail in iron(II) sulfate (FeSO4) solution.
Both nails are cleaned with sandpaper, placed in each solution, and the test tubes are stoppered and left overnight.
(a) Describe any observations that would be made the next day.
(b) (i) Identify the type of reaction that occurs and give a reason for your choice. You may refer to the activity series provided in the resource booklet.
(ii) Write a balanced ionic equation for ONE reaction that occurs.
Cleaned pieces of the metals iron (Fe), lead (Pb) and tin (Sn) were placed in solutions of iron(II) sulfate (FeSO4), lead nitrate (Pb(NO3)2) and tin sulfate (SnSO4), as shown in the table below:
A piece of copper wire placed in a solution of silver nitrate undergoes a displacement reaction.
Give a detailed account of this reaction. You may refer to the Activity series in the Resource Booklet.
In your answer you should:
• describe any observations that would be made
• link these observations to the chemical species involved
• explain why the displacement reaction occurs
• write a balanced ionic equation for this reaction.
A clean iron nail placed in a solution of copper (II) sulfate undergoes a displacement reaction over a period of time.
Discuss the chemistry of this displacement reaction. In your answer, you should:
describe the physical changes that would occur
relate each change to the chemical(s) involved
fully explain why the displacement reaction occurs
write a balanced ionic equation for the reaction.
Some grey powdered magnesium was added to a green solution of iron (II) sulfate in a beaker, and mixed well. The green colour of the solution faded and the grey powder disappeared. A new dark grey solid formed on the bottom of the beaker.
(i) State what type of reaction this is.
(ii) Discuss what happened in this reaction. Your answer should link the reactants and products involved in the reaction to the observations made.
Include an appropriate balanced equation in your answer. Spectator ions may be omitted.
1) aluminium + silver nitrate → _ + __
2) A piece of zinc foil is added to copper (II) nitrate solution and left. It is checked after 10 minutes and then again after 24 hours.
(i) Describe ONE observation that you would expect to make after 10 minutes.
(ii) Describe a different observation that you would expect to make after 24 hours.
(iii) Explain why BOTH of your observations above have occurred.
(iv) Write a balanced equation for this reaction. Spectator ions may be omitted.
A piece of copper is placed in a solution of silver nitrate.
COMBINATION REACTIONS
reactions of elements with other elements
NCEA PAST EXAM QUESTIONS on Combination
Two reactions that burn brightly were shown to a class. In Reaction 1, the teacher demonstrated a strip of magnesium ribbon reacting with oxygen in air.
In Reaction 2, which was shown on a video, a grey powder, zinc, was mixed with yellow sulfur powder. The mixture was poured into a pile and heated. The mixed powders burst into flame and made a white powder. Analyse these reactions by answering the following questions.
(a) Identify the type of reaction occurring, and state the condition that both reactions require for each to occur.
(b) Reaction 1: Magnesium metal reacting with oxygen gas in air.
(i) Describe the observations that would be made for this reaction.
(ii) Link these observations to the reactants and products involved in this reaction.
Reaction 2: Zinc metal reacting with sulfur.
(iii) Name the product formed when powdered sulfur reacts with powdered zinc metal.
(iv) Link the observations for this reaction, as given above, to the reactants and products involved.
(c) Explain the two reactions (magnesium ribbon with oxygen gas, and zinc powder with sulfur powder) in terms of electron transfer.
Write a balanced symbol equation for each reaction.
A teacher showed her class two video clips of chemical reactions. One was of a reaction between sodium metal and chlorine gas. The second was of a reaction between solid sulfur and chlorine gas.
(a) When the sodium metal reacted with chlorine gas, the video clip showed a shiny grey solid reacting with a yellow-green gas. The reaction resulted in the formation of white crystals. Link these observations to the reactants and products involved in this reaction.
(i) Name the product that will be formed when solid sulfur reacts with chlorine gas.
(ii) Identify the type of reaction that is occurring, and give a reason for your choice.
(b) (i) Write a balanced symbol equation for the reaction between sodium and chlorine.
(ii) Write a balanced symbol equation for the reaction between sulfur and chlorine.
(c) Explain the differences in the two reactions: sodium with chlorine gas and sulfur with chlorine gas, in terms of electron transfer.
A teacher demonstrates a reaction between hydrogen gas and oxygen in the air.
(i) Identify the type of reaction that occurs: Give a reason for your choice:
(ii) Describe any observations that would be made of this reaction, and link these to the substances involved in the reaction. Outline a test that could be used to confirm the presence of the product formed.
(iii) Write a balanced symbol equation for this reaction.
Different elements can be reacted together to form compounds with properties that are different to the original elements.
The reaction of iron and sulfur to form iron(II) sulfide is an example of a combination reaction where all species (reactants and products) have different properties. Give a detailed account of this combination reaction.
In your answer you should:
state the conditions required for this reaction to occur
describe any observations that would be made
outline the physical and chemical properties of EACH of the species
explain why the properties of the reactants differ from those of the products
write a balanced symbol equation for the reaction.
Chemical compounds are made by combining elements. For example, magnesium oxide is made by combining magnesium and oxygen, and carbon dioxide is made by combining carbon and oxygen.
Compare and contrast the combination reaction that produces magnesium oxide with the combination reaction that produces carbon dioxide. In your answer, you should:
state the conditions required for EACH combination reaction to occur
describe what would be observed in EACH combination reaction
write a balanced symbol equation for EACH combination reaction
discuss the similarities and differences between the TWO combination reactions.
EXCHANGE/PRECIPITATION REACTIONS
chlorides and iodides of silver and lead
sulfates of calcium, barium and lead
hydroxides of copper, iron(II), calcium, barium and magnesium
carbonates of copper, iron(II), calcium, barium, magnesium, zinc, and lead.
NCEA PAST EXAM QUESTIONS on Exchange/Precipitation reactions
Various solutions were mixed in three separate beakers. Only two of the mixtures produced precipitates.
Identify the name, formula and colour of any precipitate that may have formed in the beakers
Justify the formation, or lack of formation, of precipitates in each of the three beakers. In your answer you should:
• identify the ions present in each solution before they are mixed
• explain why precipitates form or do not form
• write a balanced ionic or symbol equation for each of the precipitates formed.
You may leave spectator ions out of your equations.
An experiment in a school laboratory involves adding colourless solutions together as shown in the diagram below.
• record any observations you would make, and link these observations to the products formed in each reaction
• identify the type of reaction occurring in test tube A and test tube B, and justify your choices
• write a balanced ionic equation for each reaction.
The water in a swimming pool contains chloride ions as a result of adding chlorine to help keep the water safe to swim in.
Outline how you could test that there are chloride ions in the swimming pool. In your answer you should:
• describe what you would do to test for chloride ions
• identify the type of reaction and explain how this reaction helps identify the chloride ions
• describe all observations and link these to the chemical species involved
• write a balanced ionic equation for the reaction.
A chemical reaction occurs when a solution of calcium nitrate is added to a solution of sodium hydroxide. Analyse this reaction by:
describing any observations that would be made
identifying the products
explaining what happens to EACH ion that is present in these two solutions
writing a balanced symbol equation for this reaction. (Spectator ions may be omitted.)
Two solutions are mixed in one beaker and two different solutions are mixed in another beaker, as shown below. A precipitate forms in one of the beakers.
Identify the beaker in which a precipitate would form and justify your choice. In your answer, you should:
state which beaker the precipitate would form in
name the ions present in that beaker before they are mixed
name the precipitate formed (use the solubility rules in the resource booklet)
write a balanced symbol equation for the precipitation reaction
fully explain why no other precipitate will form in that beaker.
When a fresh solution of iron(II) sulfate is added to a solution of potassium carbonate, a precipitate forms. Discuss the process of this precipitation reaction.
FeSO4(aq) + K2CO3(aq) → ?In your answer:
- State any observations you would make.
- Explain what happens to each ion present in the solutions used in this reaction.
- Write the name or formula of the precipitate formed.
- Write a balanced equation (spectator ions may be omitted).
Refer to the solubility rules provided in the Resource Booklet.Discuss what happens when a solution of potassium hydroxide is added to a solution of calcium nitrate.
KOH(aq) + Ca(NO3)2(aq) → ?In your answer:
describe the observations you would make
predict the products that will form
explain what happens to each ion present in the solutions used in this reaction
write a net ionic equation for the precipitation reaction.
Each of the following equations shows what could happen when two solutions are mixed in a beaker.
Reaction 1 Pb(NO3)2 + 2NaCl → PbCl2 + 2NaNO3Reaction 2 FeSO4 + Mg(NO3)2 → Fe(NO3)2 + MgSO4Use the solubility rules in your Resource Booklet to identify which reaction would form a precipitate. Justify your answer by:
identifying the ions present in each solution before they are mixed
identifying the precipitate formed when the solutions are mixed
explaining why that precipitate forms.
1) The following pairs of solutions are mixed. Use the solubility rules in your Resource Booklet to identify if a precipitate is formed.
(a) Write the name of the precipitate. If none is formed, write no precipitate.
(b) Write a balanced equation for the formation of ONE precipitate identified in (a) above. Spectator ions may be omitted from ionic equations.
2) lead nitrate + potassium chloride → +3) A colourless solution of barium nitrate is added to a pale green solution of iron(II) sulfate in a beaker. A reaction occurs.
(a) Describe the observations that would be expected for this reaction.
(b) State what type of reaction is occurring.
(c) Discuss the chemistry of this reaction. Your discussion should refer to the observations you made in part (a). Include a balanced equation in your answer. Spectator ions may be omitted.
The following solutions are mixed in the pairs shown. Use the solubility rules in your Resource Booklet to identify the precipitate (if any) that is formed for each pair.
(a) Write the name of the precipitate or, if none is formed, write no precipitate.
(b) Write a balanced equation for the formation of ONE precipitate identified in question (a)above. Spectator ions may be omitted from ionic equations.
The following pairs of solutions are mixed. Use the solubility rules in your Resource Booklet to identify the precipitate (if any) that is formed. Write the name of the precipitate or, if none is formed, write no precipitate.
Write a balanced equation for the formation of ONE precipitate identified in question (a) above. Spectator ions may be omitted from ionic equations.
magnesium chloride + sodium hydroxide → + _Iron (II) nitrate solution is added to sodium hydroxide solution in a test tube. (i) Describe ONE observation that you would make as the reaction occurs.
(ii) Explain why your observation occurred.
(iii) Write a balanced ionic equation for this reaction.
1) Complete the table below by writing the name of the precipitate, or no precipitate if one is not formed. Use the Solubility Rules in the Resource Booklet.
2) A solution of sodium hydroxide is added to a solution of iron (III) chloride.
(i) Describe ONE observation that would be made:
(ii) Write a balanced equation for this reaction:
DECOMPOSITION REACTIONS
thermal decomposition of hydroxides, carbonates and hydrogen carbonates
catalytic decomposition of hydrogen peroxide
NCEA PAST EXAM QUESTIONS on Decomposition
Two decomposition reactions were set up in the laboratory.
Reaction 1: Solid sodium hydrogen carbonate, NaHCO3, was heated over a Bunsen burner flame.
Describe any observations that would be made as this reaction occurs, and link these to the reactants and products involved in the reaction.
(ii) Outline a test that could be used to confirm the presence of one of the products formed.
Write a balanced symbol equation for the decomposition of sodium hydrogen carbonate, NaHCO3.
Reaction 2: Test tube 1 and test tube 2 were both half-filled with hydrogen peroxide solution, H2O2. Some powdered manganese dioxide, MnO2, was then added to test tube 1.(c) Compare the observations you would make for the reactions in the two test tubes.
Link these observations to the reactants and products involved in the reactions.
(d) Write a balanced symbol equation for the reaction in test tube 1.
Compare and contrast the decomposition reactions shown in Reaction 1 (sodium hydrogen carbonate, NaHCO3) and Reaction 2 (hydrogen peroxide, H2O2).
Two calcium compounds were heated over a Bunsen burner in a school laboratory. In the first experiment, shown in the diagram below, calcium carbonate was heated. In the second experiment, calcium hydroxide was heated.
Compare and contrast the reaction that occurs when solid calcium carbonate is strongly heated, with the reaction that occurs when solid calcium hydroxide is strongly heated. In your answer:
• identify the type of reaction that occurs when each substance is strongly heated, and justify your choice
• describe any observations that would be made in each reaction, and link these observations to the reactants and products involved
• explain how the gas formed in each reaction could be identified
• write a balanced symbol equation for each reaction.
1) In a reaction, a boiling tube with copper carbonate powder is heated over a Bunsen burner flame.
(i) Identify the type of reaction that occurs: Give a reason for your choice:
(ii) Describe any observations that would be made of this reaction, and link these to the substances involved in the reaction.
Outline a test that could be used to confirm the presence of ONE of the products formed.
(iii) Write a balanced symbol equation for this reaction.
2) Two test tubes were set up in a school laboratory. Both test tubes were half-filled with identical solutions of hydrogen peroxide (H2O2).
It was observed that a few small bubbles of a colourless gas formed on the sides of each test tube.
Some solid manganese dioxide (MnO2) was added to test tube B.
(a) Describe the observations you would make after manganese dioxide (MnO2) was added to test tube B.
(b) Explain the chemistry of this reaction. In your answer you should:
• identify the type of reaction that happens in test tube B
• justify your choice of the type of reaction
• link the observations made for the reaction in test tube B to the substances involved in the reaction
• write a balanced symbol equation for the reaction involving hydrogen peroxide.
Students in a laboratory are asked to identify three powders by using a thermal decomposition reaction. The powders are copper hydroxide, Cu(OH)2, sodium carbonate, Na2CO3, and sodium hydrogen carbonate, NaHCO3. Explain how you could identify each of these powders by heating them.
Your answer should include:
any observations that would be made
any tests that would be carried out on products formed to confirm their presence
balanced symbol equations for any reactions occurring.
1) A group of students carried out an investigation into whether or not various solid carbonates undergo thermal decomposition. The students found that copper (II) carbonate did decompose when heated. Discuss the thermal decomposition of copper (II) carbonate. In your answer, you should:
name the products formed
describe what would be observed during the decomposition
explain why a solution of limewater would be useful in this investigation
fully explain what happens to the carbonate ions in the decomposition reaction
write a balanced chemical equation for the decomposition reaction.
2) A solution of hydrogen peroxide decomposes into water and oxygen gas very slowly.A catalyst can be used to speed up this reaction. The sketch graph below shows the volume of oxygen produced over the course of time when a catalyst is use
Discuss the decomposition of hydrogen peroxide using a catalyst. In your answer, you should:
name a catalyst that would be suitable for this reaction
describe what would be observed during the decomposition reaction
explain why only a small amount of catalyst is needed to catalyse this decomposition reaction
fully explain what happens in the catalytic decomposition of hydrogen peroxide over time as shown in the graph above.
Three carbonate compounds, sodium carbonate, zinc carbonate and copper carbonate, are heated one at a time in the apparatus shown in the diagram below.
(a) Complete the following table for the above reactions.
(b) Discuss the differences in the decomposition of sodium carbonate, zinc carbonate, and copper carbonate.
Describe the differences between the reactions of the three carbonates.
Link the relevant species to the observations you recorded in the table in (a).
Include any balanced equations.
Some green copper(II) carbonate powder is heated in a boiling tube over a Bunsen flame. A burning splint inserted into the top of the boiling tube goes out.
Discuss the chemistry in this thermal decomposition reaction by:
describing ONE other observation that would be made during this reaction
linking the observations to the relevant chemical species
writing a balanced equation.
Some dry copper(II) hydroxide was heated in a test tube over a Bunsen burner. When a piece of blue cobalt chloride paper was held in the mouth of the test tube, the paper turned pink. Discuss what happened in the reaction in the test tube.
Your answer should include any observations that would occur, and link all the observations to the reactants and products involved. Include an appropriate balanced equation in your answer.
A small amount of zinc hydroxide is heated in a test tube over a Bunsen burner. The following reaction occurs.
(a) State what type of reaction is occurring.
(b) Fully describe the observations that would be expected if this reaction was carried out in a school laboratory. Remember to link your observations to the substances involved.
A group of students carried out an investigation into the thermal decomposition of the following solid carbonates: sodium carbonate, calcium carbonate, and copper carbonate.
(a) Describe the appearance of each carbonate before it was heated.
(b) Describe the observations the students would have made when heating each of the carbonates.
(c) Write a balanced equation for the thermal decomposition of copper carbonate.
1) copper hydroxide (heat) →
2) A sample of copper carbonate is heated strongly in a boiling tube fitted with a delivery tube. The gas formed is bubbled into limewater. (See the diagram below.)
(i) Describe TWO observations, other than bubbles of gas, that would be made:
(ii) Write a balanced equation for the reaction that occurs when copper carbonate is heated:
DISPLACEMENT REACTIONS
displacement of metals ions in solution by other metals
NCEA PAST EXAM QUESTIONS on Displacement
A zinc rod was placed in a solution of copper sulfate, and another zinc rod was placed in a solution of magnesium sulfate. Both were left for one week
Describe any observations that would be made for each beaker. Identify the type of reaction that is occurring above.
Explain any difference in the observations made in Beaker 1 and Beaker 2 by linking your observations to the type of reaction occurring, and the reactants and products involved. Write ONE balanced ionic equation for a reaction from (a).
In the laboratory the teacher made impure lead crystals by placing a metal in lead nitrate solution
(i) Choose a suitable metal for this reaction and justify your choice.
(ii) Write a balanced ionic equation for the reaction you have chosen above
A spotting tile was set up, as shown in the diagram below, to investigate the reaction of small pieces of cleaned metals with a small volume of different metal nitrate solutions.
Complete the table below to identify which reactions will occur. You may refer to the activity series in the resource booklet.
identify the reaction you have selected
describe any observations that would be made in the selected reaction, and link your observations to the reactants and products involved in the reaction
identify the type of reaction occurring, and justify your choice write a balanced symbol equation for your reaction.
Explain why magnesium nitrate solution does not react with any of the three metals zinc, copper and lead.
You may refer to the activity series in the resource booklet.
An experiment in the laboratory involves placing an iron nail in copper sulfate (CuSO4) solution and a copper nail in iron(II) sulfate (FeSO4) solution.
Both nails are cleaned with sandpaper, placed in each solution, and the test tubes are stoppered and left overnight.
(a) Describe any observations that would be made the next day.
(b) (i) Identify the type of reaction that occurs and give a reason for your choice. You may refer to the activity series provided in the resource booklet.
(ii) Write a balanced ionic equation for ONE reaction that occurs.
Cleaned pieces of the metals iron (Fe), lead (Pb) and tin (Sn) were placed in solutions of iron(II) sulfate (FeSO4), lead nitrate (Pb(NO3)2) and tin sulfate (SnSO4), as shown in the table below:
A piece of copper wire placed in a solution of silver nitrate undergoes a displacement reaction.
Give a detailed account of this reaction. You may refer to the Activity series in the Resource Booklet.
In your answer you should:
• describe any observations that would be made
• link these observations to the chemical species involved
• explain why the displacement reaction occurs
• write a balanced ionic equation for this reaction.
A clean iron nail placed in a solution of copper (II) sulfate undergoes a displacement reaction over a period of time.
Discuss the chemistry of this displacement reaction. In your answer, you should:
describe the physical changes that would occur
relate each change to the chemical(s) involved
fully explain why the displacement reaction occurs
write a balanced ionic equation for the reaction.
Some grey powdered magnesium was added to a green solution of iron (II) sulfate in a beaker, and mixed well. The green colour of the solution faded and the grey powder disappeared. A new dark grey solid formed on the bottom of the beaker.
(i) State what type of reaction this is.
(ii) Discuss what happened in this reaction. Your answer should link the reactants and products involved in the reaction to the observations made.
Include an appropriate balanced equation in your answer. Spectator ions may be omitted.
1) aluminium + silver nitrate → _ + __
2) A piece of zinc foil is added to copper (II) nitrate solution and left. It is checked after 10 minutes and then again after 24 hours.
(i) Describe ONE observation that you would expect to make after 10 minutes.
(ii) Describe a different observation that you would expect to make after 24 hours.
(iii) Explain why BOTH of your observations above have occurred.
(iv) Write a balanced equation for this reaction. Spectator ions may be omitted.
A piece of copper is placed in a solution of silver nitrate.
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